1. Field of the Invention
The invention pertains to devices, such as milling tools and/or a roller mill, for grinding or comminuting fiber or fibrous material wherein the milling tools comprise at least one pair of opposed relatively movable and substantially rotationally symmetrical milling tool carriers, including a rotor and a stator, upon which carriers the milling tools are so attachable in pairs and that the milling tools form least one pair of complementary working surfaces; the working surfaces in turn forming a milling aperture, with the fibrous material flowing through the milling aperture during the operation of the roller mill; and the working surface of at least one milling tool, on the side facing the fibrous material, during operation, including above base surface of he working surfaces, a plurality of raised areas acting in the manner of knives, with the raised areas having channel shaped slots so that the fibrous material can at least be partially directed through the slot from the inside to the outside thereof, with a mechanical working of the fibrous material being achieved via the relative motion between the complementary working surfaces.
2. Discussion of the Background of the Invention and Material Information
Milling tools of the previously described type which are also often denominated as garnitures, are incorporated in roller mills that are also often denominated as refiners. Such roller mills include at least one rotor and at least one stator with either disk-shaped or conically formed surfaces which are adapted to receive the milling tools or garnitures in a manner so as that a milling or comminution aperture is formed therebetween. The milling tools under consideration here include webs or fillets and slots or grooves at the working surfaces and are thus also referred to as "knife garnitures".
A substantial part of the operating costs incurred in the grinding or comminution of fiber or fibrous materials in the wood pulp, cellulose, and paper industry are due to energy costs. Thus, it has always been an endeavor to build and operate devices of this type which, as measured relative to the desired result, do not require excessive energy utilization. Since the targets of fibrous material treatment differ, depending upon the application situation, the judgment or evaluation of the milling effect also differs. In many instances the utilized energy is so referred to the milling result in that either the amount per ton of fibrous material and the increase in the degree of fineness or the kilowatt hour per ton of fibrous material and the increase in the fiber strength is stated. The compatibility of such values however otherwise requires the same operating conditions. In particular, it is not possible to lower the grinding costs in that while lower energy is utilized, on the other hand, even with a sufficient increase in the degree of fineness, the treated fibrous material no longer meets quality requirements.